Defect review apparatus and method of reviewing defects

ABSTRACT

A defect review apparatus for reviewing a specimen by moving the specimen to pre-calculated coordinate includes: a function to measure a deviation amount between the pre-calculated coordinates and coordinates of an actual position of the specimen; a function to optimize a coordinate correcting expression to minimize the measured deviation amount; and a function to determine that the deviation amounts have converged. When the deviation amounts have converged, the measurement for the coordinate-correcting-expression optimization is terminated, minimizing a reduction in throughput. field of view (FOV) necessary for the specimen to be within the FOV is set according to a convergence value of the calculated deviation amount.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a review apparatus for reviewing aspecimen by moving a specimen stage to designated coordinates. Inparticular, the present invention relates to a defect review apparatus,as in a scanning electron microscope (SEM) defect review apparatus, fordetermining a review position by an automatic defect review (ADR) on thebasis of information on a defect position detected by an inspectionapparatus in an upper level.

The present invention also relates to a method and a review apparatusfor setting a field of view for reviewing to have the optimum size bycorrecting designated coordinates and observation coordinates so that aspecimen can be within the field of view for reviewing in order toachieve both high throughput and high accuracy of detecting a positionof the specimen.

2. Description of the Related Art

In order to secure a high yield rate, for example, in a semiconductorfabrication process, it is important to find a defect, which occurs inthe fabrication process, as early as possible to take appropriatemeasures against the defect as soon as possible. Nowadays, semiconductordevices are so miniaturized that even a minute defect may cause nolonger negligible influence on the yield rate. For this reason, muchsmaller defects must be checked to avoid the yield rate decrease. An SEMdefect review apparatus is one of important apparatuses for reviewingsuch a minute defect. In general, this kind of apparatus reviews adefect on the basis of the defect position detected in advance by anupper-level inspection apparatus such as an optical microscope andanother SEM apparatus. When the defect is reviewed manually, a specimenstage is moved to the coordinates that are designated in an output fromthe upper-level inspection apparatus. Then, the specimen is imaged at alow magnification level at which the specimen can come within the fieldof view. After the defection position is visually checked, the stage ismoved in a way that the defect position comes to the center of the fieldof view so as to acquire a defect image for reviewing at a highmagnification. The apparatus having these steps automated is anautomatic defect review (ADR).

The ADR performs image processing on a low magnification image fordetecting a defect position (hereinafter, referred to as a “monitoringimage”) to detect a defect appearing within the field of view of themonitoring image. A specimen stage is moved so that the detected defectcan come to the center of the field of view. Subsequently, an image forreviewing (hereinafter, referred to as “review image”) is obtained at ahigh magnification that allows the defect to be detected easily indetails. From the viewpoint of performing image processing, it ispreferable to capture a monitoring image at a higher magnification tomake the defect larger for reviewing. Nevertheless, if the magnificationis too high, it is more likely that some defect would be outside thefield of view (hereinafter, referred to as “view-field displacement”).For this reason, among the setting for the ADR, the setting of themagnification for the monitoring image is dependent on the experience ofthe user, and the magnification is a difficult parameter to set.

In particular, as a means for achieving both the detection of such aminute defect and the prevention of the view-field displacementtogether, there has been recently employed a method of enlarging thesize of the field of view for reviewing without changing themagnification. However, this method requires the user to set themagnification for the monitoring image and the size of the field of viewin combination, and thus produces a problem that it is even moredifficult to set these parameters than otherwise.

As a method for effectively performing the magnification settingoperation for the monitoring image, Japanese Patent ApplicationPublication No. 2001-338601 (Patent Document 1) discloses a method inwhich a coordinate correcting expression is optimized so as to minimizethe amounts of deviation between a defect position outputted from anupper-level inspection apparatus and an actually detected defectposition. Moreover, Japanese Patent Application Publication No.2002-131253 (Patent Document 2) discloses a method in which themagnification of the monitoring image is optimized on the basis ofdetected deviation amounts.

SUMMARY OF THE INVENTION

According to the method disclosed in Patent Document 1, it is possibleto set a searching magnification according to the deviation amountsmeasured on the basis of the optimized coordinate correcting expression.

Nevertheless, when the upper-level inspection apparatus provides onlylow coordinate detection accuracy, the method in Patent Document 1 canproduce only a small effect on the correction. For this reason, beforethe SEM performs the ADR in the SEM defect review apparatus, all thedefect positions to be reviewed are generally detected by using, forexample, an optical microscope which belongs to the review apparatus,and which is capable of detecting the defect position more rapidly thanthe SEM. When all the defect positions are detected and reviewed asdescribed above, the throughput is considerably reduced. Accordingly,there is a demand for the development of a method of optimizing thecoordinate correcting expression with processing load reduced to theminimum required level.

Moreover, a means for evaluating the correction effect is not preparedfor the conventional techniques described above. Hence, even in the casewhere the measuring the deviation amounts at only several points isenough to produce a sufficient correction effect through the coordinatecorrecting expression optimization, the measurement has to continueuntil all a predetermined number of deviation amounts are measured.Accordingly, even in the case of using the aforementioned inspectionapparatus can provide accurate coordinates, there is a demand for thedevelopment of the method of optimizing the coordinate correctingexpression with processing load reduced to the minimum required level.

Furthermore, the coordinate detection accuracy varies to a large extent,depending on the type and state of the upper-level inspection apparatus.Accordingly, if the coordinates are uniformly corrected in the sameprocess, the coordinate correction accuracy varies. With suchvariations, even a skilled person has a difficulty in setting acombination of the magnification for a monitoring image and the size ofthe field of view for reviewing so as to make the specimen be within thefield of view for reviewing and concurrently to make the magnificationas high as possible to improve the ADR detection accuracy. Thus, it issought to devise a mechanism which allows any user to perform suchsetting easily.

An object of the present invention is to suppress the reduction inthroughput for reviewing defects by simplifying a measurement operationof deviation amounts to the minimum required level. Another object ofthe present invention is to optimize the size of a field of view forreviewing on a monitoring image.

In order to solve the above problems, an aspect of the present inventionprovides a defect review apparatus for reviewing a defect on a specimen,the apparatus including: an optical detector which detects the defect onthe basis of information on coordinates of the defect, the informationtransmitted from an external apparatus; and a calculator whichcalculates a difference between the information on the coordinates andcoordinates of the detected defect, and which determines to continue thecalculation of the difference when the value of the difference issmaller than a predetermined value.

According to another aspect of the present invention, a defect reviewapparatus for reviewing a defect on a specimen includes: a displaydevice which displays an image of the specimen at a predetermined sizeof a field of view; an optical detector which detects the defect on thebasis of information on coordinates of the defect, the informationtransmitted from an external apparatus; and a calculator whichcalculates a difference between the information on the coordinates andcoordinates of the detected defect, and which determines to continue thecalculation of the difference on the basis of a reference valuedetermined depending on the value of the difference and the size of thefield of view.

According to another aspect of the present invention, a defect reviewapparatus for reviewing a defect on a specimen includes: a displaydevice which displays an image of the specimen at a predetermined sizeof a field of view; an optical detector which detects the defect on thebasis of information on coordinates of the defect, the informationtransmitted from an external apparatus; and a calculator whichcalculates a difference between the information on the coordinates andcoordinates of the detected defect, and the calculation of thedifference is determines to be continued when the value of thedifference calculated by the calculator is within a reference valuedetermined on the basis of a size of a field of view.

According to another aspect of the present invention, a defect reviewapparatus for reviewing a defect on a specimen includes: a displaydevice which displays an image of the specimen at a predetermined sizeof a field of view; an optical detector which detects the defect on thebasis of information on coordinates of the defect, the informationtransmitted from an external apparatus; and a calculator whichcalculates a difference between the information on the coordinates andcoordinates of the detected defect, and which determines to continue thecalculation of the difference when the defect appears in the image ofthe specimen displayed on the display device.

According to another aspect of the present invention, a defect reviewapparatus for reviewing a defect on a specimen by moving the specimen toa pre-calculated coordinate position in a first coordinate system tospecify a position of the specimen by a second coordinate systemincludes: a deviation-amount measurement unit which measures a deviationamount between the pre-calculated coordinate position and an actualposition of the specimen; a coordinate-correcting-expression optimizingunit which optimizes a coordinate correcting expression for convertingthe second coordinate system to the first coordinate system so as tominimize the measured deviation amount; and adeviation-amount-convergence determination unit which determines thatthe deviation amount has converged, and the measurement for optimizingthe coordinate correcting expression is terminated when the deviationamount has converged.

According to another aspect of the present invention, a defect reviewapparatus for reviewing a defect on a specimen by moving the specimen toa pre-calculated coordinate position in a first coordinate system tospecify a position of the specimen by a second coordinate systemincludes: a deviation-amount measurement unit which measures a deviationamount between the pre-calculated coordinate position and an actualposition of the specimen; a coordinate-correcting-expression optimizingunit which optimizes a coordinate correcting expression for convertingthe second coordinate system to the first coordinate system so as tominimize the measured deviation amount; and adeviation-amount-convergence determination unit which determines thatthe deviation amount has converged, and the measurement for optimizingthe coordinate correcting expression is terminated at a time when aconvergence value of the deviation amount is equal to or less than apredetermined value.

According to another aspect of the present invention, provided is amethod of reviewing a defect on a specimen by moving the specimen to apre-calculated coordinate position in a first coordinate system tospecify a position of the specimen by a second coordinate system, themethod including the following steps of: measuring a deviation amountbetween the coordinate position in the first coordinate system and acoordinate position in the second coordinate system, and starting finealignment process for optimizing a coordinate correcting expression soas to minimize the deviation amount; repeating a procedure foroptimizing the coordinate correcting expression and concurrently formeasuring a deviation between coordinates corrected on the basis of thecoordinate correcting expression and coordinates of a position of thespecimen actually detected; determining that the deviation amount hasconverged; and continuing the fine alignment process when the deviationamount has not converged, and setting a field of view for reviewing tobe equal to or greater than a convergence value of the deviation,terminating the fine alignment process, and starting an ADR, when thedeviation amount has converged.

It is preferable that the method of reviewing a defect further includethe steps of: comparing the convergence value of the deviation amountwith a FOV in terms of size; and terminating the fine alignment processand starting the ADR when the convergence value of the deviation amountis equal to or less than the FOV, and enlarging the FOV of the ADR witha reviewing magnification maintained when the convergence value isgreater than the set FOV.

The present invention may be a program which causes a computer toexecute the above-described steps, or may be a computer-readable storagemedium storing the program therein.

According to the present invention, the measurement for optimizing thecoordinate correcting expression is terminated when the deviation amounthas converged by using the coordinate correcting expression. Thereby,the reduction in the throughput is suppressed to the minimum level.

Furthermore, a FOV which is necessary for a specimen to be within thefield of view for reviewing is automatically set according to thecalculated convergence value of the deviation amounts. Thereby, it ispossible to reduce the frequency of failure in detecting specimenpositions caused by an incident that the specimen is not within thefield of view at the time of performing the ADR.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a basic configuration of a SEMsemiconductor defect review apparatus according to one embodiment of thepresent invention.

FIG. 2 is a flowchart showing a process flow for a terminationdetermination of a fine alignment process and a FOV optimizationaccording to this embodiment.

FIG. 3 is a flowchart for the termination determination of the finealignment process, the FOV optimization, and an optimization of aperipheral searching setting.

FIG. 4 is a diagram showing the relationship between an image size andthe peripheral searching setting.

FIG. 5 is a diagram showing the relationship among the number of thefine alignment process performed, deviation amounts, and the FOV.

FIG. 6 shows an example of a GUI for analyzing the fine alignment andfor setting the FOV.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This application is based on the Japanese Patent applicationJP2007-117254, all the contents of which is incorporated in thisapplication by reference.

Hereinafter, description will be given of a defect review apparatusaccording to one embodiment of the present invention with reference todrawings. FIG. 1 is a cross-sectional view showing a configurationexample of a SEM defect review apparatus according to this embodiment.The SEM defect review apparatus shown in FIG. 1 includes an electron gun101, a lens 102, a deflector 103, an objective lens 104, a specimen 105,a stage 106, a secondary particle detector 109, an electro-opticalsystem controller 110, an A/D converter 111, a stage controller 112, awhole controller 113, an image processor 114, a display 115, a keyboard116, a storage 117, a mouse 118 and an optical microscope 119. Anelectron beam 107 emitted from the electron gun 101 is focused by thelens 102, deflected by the deflector 103, and then focused by theobjective lens 104 before the electron beam 107 irradiates the specimen105. The specimen 105 thus irradiated with the electron beam 107generates a secondary particle 108 such as a secondary electron and areflection electron, depending on the shape and material of thespecimen. The secondary particle 108 thus generated is detected by thesecondary particle detector 109, converted into a digital signal by theA/D converter 111, and thereby a SEM image is formed. Using the SEMimage thus formed, the image processor 114 performs image processing fordetecting a defect and the like. The lens 102, the deflector 103, andthe objective lens 104 are controlled by the electro-optical systemcontroller 110. The position of the specimen is adjusted by the stage106 that is controlled by the stage controller 112. The whole controller113 interprets an input signal transmitted from the keyboard 116, thestorage 117, the mouse 118, and controls the electro-optical systemcontroller 110, the stage controller 112, the image processor 114, andthe like. If necessary, the whole controller 113 outputs the contents ofprocessing to the display 115 and the storage 117.

FIG. 2 is a flowchart showing a process flow for suppressing a reductionin the throughput of the apparatus by minimizing the measurement of adeviation amount, and for optimizing a size of a field of view forreviewing (hereinafter, referred to as FOV). Firstly, fine alignmentprocess is started (S201) prior to an ADR. In the fine alignmentprocess, a coordinate correcting expression is optimized so as tominimize a deviation amount (i.e., a difference in coordinates) whichhas been calculated. The deviation amount is a difference between aposition of a specimen outputted by an upper-level inspection apparatus,and that actually detected by the review apparatus. In Step S201 of thefine alignment process, Step 202 and S203 are repeatedly executed. InStep 202, a deviation is measured between coordinates correctedaccording to the coordinate correcting expression and that of a positionof the specimen actually detected. Thereafter in Step 203, thecoordinate correcting expression is optimized.

Incidentally, the following formula can be used as an example of thecoordinate correcting expression.

For example, as described in Patent Document 1, in a case where factorsof a coordinate error are an origin offset (a, b), a rotating error β,dimensional accuracy errors m and n of the respective x- and y-axes, anda perpendicularity error α of the coordinate axes, the coordinateconverting expression is represented by the following Formula (1):

$\begin{matrix}{\begin{pmatrix}x \\y\end{pmatrix} = {{\begin{pmatrix}{m\left( {{\cos\;\beta} + {\sin\;\beta\;\tan\;\alpha}} \right)} & {- \frac{n\;\sin\;\beta}{\cos\;\alpha}} \\{m\left( {{\sin\;\beta} - {\cos\;\beta\;\tan\;\alpha}} \right)} & \frac{n\;\cos\;\beta}{\cos\;\alpha}\end{pmatrix}\begin{pmatrix}x_{3} \\y_{1}\end{pmatrix}} + \begin{pmatrix}a \\b\end{pmatrix}}} & (1)\end{matrix}$where

-   (x1, y1): coordinates of an object, measured by an object inspection    apparatus,-   (x, y): coordinates of the object, converted for a SEM coordinates    system,-   (a, b): an error of the coordinate origin of the object inspection    apparatus,-   m: a dimensional accuracy error of the x-axis of the object    inspection apparatus,-   n: a dimensional accuracy error of the y-axis of the object    inspection apparatus,-   α: a perpendicularity error of coordinates of the object inspection    apparatus, and-   β: an angular error between the coordinate axes.

The coordinate converting expression is created by determining theparameters a, b, m, n, α and β by using a method of least squares sothat the coordinates (x1, y1) of the object measured by the objectinspection apparatus may be equal to the coordinates (x, y) of theobject measured by the SEM with high accuracy. The resulting coordinateconverting expression is used to correct the coordinates from the objectinspection apparatus to those for the SEM. This correction can beperformed, for example, by software in a computer.

As the coordinate correcting expression, the following formulas asdescribed in Patent Document 2 may be used:dX=a+b*X−c*Y  (2)dY=d+e*Y+f*X  (3)where

-   dX: a position correction amount in the x-axis direction,-   dY: a position correction amount in the y-axis direction,-   X: a defect position in the x-axis direction in a coordinate    detection system,-   Y: a defect position in the y-axis direction in the coordinate    detection system,-   a: a constant for an offset component in the x-axis direction of a    coordinate review system, with respect to the coordinate detection    system,-   b: a constant (coefficient) for a magnification component in the    x-axis direction of the coordinate review system, with respect to    the coordinate detection system,-   c: a constant (coefficient) for a rotation component in the x-axis    direction of the coordinate review system, with respect to the    coordinate detection system,-   d: a constant for the offset component in the y-axis direction of    the coordinate review system, with respect to the coordinate    detection system,-   e: a constant (coefficient) for the magnification component in the    y-axis direction of the coordinate review system, with respect to    the coordinate detection system, and-   f: a constant (coefficient) for the rotation component in the y-axis    direction of the coordinate review system, with respect to the    coordinate detection system.

Note that, regarding the rotation component of the coordinate reviewsystem with respect to the coordinate detection system, thecounterclockwise direction of rotation is taken to be positive.

The present defect review apparatus may have a mechanism to select anduse any of the above formulas.

The deviation may be caused by an error in a coordinate detectionaccuracy including a stage-moving accuracy of the upper-level inspectionapparatus, an error in stage-moving accuracy of the review apparatus,and the like. It is relatively easy for the review apparatus to controland correct the error in stage-moving accuracy of the review apparatus.Meanwhile, it is difficult for the review apparatus to correct the errorcaused by the various kinds of upper-level inspection apparatuses. Forthis reason, generally, the deviation amount is measured and theparameters of the coordinate correcting expression are changed in everyreview to optimize the coordinate correcting expression. Moreover, thecorrection accuracy tends to be improved by increasing the number ofmeasurement points for the deviation amount, and by increasing thenumber of optimization of the coordinate correcting expression. However,the degree of the improvement in the correction accuracy variesdepending on the type, state and setting condition of the upper-levelinspection apparatus. Thus, it is extremely difficult to determine howmany times the optimization should be repeated in advance.

Against this background, when the accuracy in coordinates designated bythe upper-level inspection apparatus is predicted to be poor, the finealignment is performed on all the objects to be reviewed so as to allowthe specimen to be surely observed rather than to improve thethroughput, in general. Note that, in this embodiment, any formula canbe used for the coordinate correcting expression. For example, the onedescribed in Patent Document 1 may be used, or other formulas may alsobe used. Next, after the deviation amounts are calculated, it isdetermined whether or not the deviation amounts have converged, and thenwhether to continue the fine alignment process (S204). When thedeviation amounts are not converged, the calculation of the deviationamount is continued in the fine alignment process (S208). When thedeviation amounts have converged, the field of view of the ADR is set tobe equal to or greater than the convergence value of the deviations(S205). Then, the fine alignment process is terminated to stop thecalculation of the deviation amount (S206), and the ADR is started(S207).

FIG. 3 is a flowchart showing a process flow for optimizing a FOV if theFOV calculated on the basis of the convergence value of the deviationamounts does not satisfy a condition for setting the FOV in theapparatus. The case where the FOV does not satisfy the condition forsetting the FOV in the apparatus means, for example, that theconvergence value is so large and greater than the maximum FOV valuesettable the apparatus. This indicates that a defect exists outside theFOV. Thus, a peripheral searching function is activated in Step S312 ofFIG. 3 to be described later.

Processes shown in Steps S301, S302, S303, S304, S306, S307 and S308 arethe same as those in Steps S201, S202, S203, S204, S206, S207 and S208of FIG. 2. In Step S305, the convergence value of the deviation amountsand the FOV are compared with each other in terms of size. When theconvergence value of the deviation amounts is equal to or less than theFOV, the fine alignment process is terminated (S306), and then the ADRis started (S307).

At this point, the present apparatus has the following advantageregarding other portions of the specimen to be reviewed. Since thedeviation amounts have converged, the other portions of the specimen tobe reviewed are expected to be within a field of view with the set FOV.Accordingly, the ADR can be performed without the fine alignmentprocess, and thus the throughput is improved. When the convergence valueis determined to be greater than the set FOV in Step 305, the FOV of theADR is enlarged while the reviewing magnification is maintained (S309).The reviewing magnification is maintained here, in order not to reducethe detection sensitivity of the ADR. To be more specific, if thereviewing magnification is reduced, the size of view to capture an imageof the same size as that without reducing the magnification is made tobe larger. However, the amount of information per pixel is reduced. As aresult, the detection sensitivity in the image processing is reduced.Thus, the image size is enlarged without reducing the reviewingmagnification. For this reason, an increasing number of reviewapparatuses are available, which have a function to capture an image ofvarious sizes. Nevertheless, due to the restriction from the hardwareand software, typically the user selects an image size among severalimage sizes which are already prepared. On the other hand, when theimage size is enlarged, it is less likely that the specimen would be outof the field of view, but the image processing time for detecting adefect is increased because the defect has to be searched out in a widefield of view. Thus, the image size cannot be enlarged freely. For thisreason, appropriate setting of an image size is a bothersome operationespecially for an inexperienced user.

After the FOV is enlarged with the reviewing magnification maintained(S309), the convergence value and the FOV enlarged in Step S309 arecompared with each other in terms of size again (S310). When theconvergence value is equal to or less than the enlarged FOV, thespecimen is expected to be reviewed within the field of view, and thusthe fine alignment process is terminated (S306), and then the ADR isstarted (S307). Meanwhile, when the convergence value is greater thanthe enlarged FOV, it is determined whether to continue the finealignment process (S311). As fine alignment is performed a larger numberof times, the deviation amount is decreased, in other words, theconvergence value tends to be small. Accordingly, the continuousiterative execution of the fine alignment process increases thelikelihood of obtaining the convergence value within the range of theFOV settable in the apparatus. In a case where the fine alignmentprocess is determined not to be continued, it is expected that thespecimen may not be within the field of view only by the singlecapturing. In this case, a peripheral searching setting is made toobserve the peripheral field of view (S312).

FIG. 4 is a schematic view for explaining an optimization process forthe peripheral searching setting in the ADR. As an example, descriptionwill be given of a case where a required pixel size is selected amongimage sizes of 512×512 pixels, 768×768 pixels and 1024×1024 pixels.

In this description, for instance, the image size is represented by S,and the number of pixels of that image is represented by a subscript. Arequired image size S_(A) is determined based on the convergence valuefrom the fine alignment, the minimum defect size to be detected and theimage processing performance. When the required image size S_(A)satisfies, for example, S₅₁₂<S_(A)<S₇₆₈ (401), the image size of the ADRis set to be S₇₆₈ (402) whose pixel number is higher in view of themargin.

Meanwhile, when a required image size S_(B), which is determined basedon the convergence value from the fine alignment, the minimum defectsize to be detected and the image processing performance, satisfiesS₁₀₂₄<S_(B) (403), the specimen may not be within the field of view onlyby the single capturing. Accordingly, it is necessary to perform thefollowing peripheral searching setting. Reference numeral 404 in FIG. 4shows an example of searching the peripheral field of view with theimages each having an image size of 512×512 pixels. Although it is alsopossible to search the periphery with image sizes of 768×768 pixels or1024×1024 pixels, the nine images each having the minimum pixel size of512×512 pixels are used to search the periphery in the reference numeral404, since the smaller image size may shorten the image processing time.As shown in the reference numeral 404, the images each having the imagesize of 512×512 pixels are disposed, centered on the image having thesame image size of 512×512 pixels, in four directions: that is,top-to-down, left-to-right and oblique directions. These images thusform a large single image of 1536×1536 pixels, which is actually dividedinto the nine images each having the image size of 512×512 pixels. Withthis operation, it becomes possible to increase the processing speed,for example, by performing the processing on the nine images each havingthe image size of 512×512 pixels simultaneously. It is also possible tosearch out a defect more rapidly by giving priority to the images in thesearching order in a way that the top priority is given to the image atthe center, and that the subsequent priorities are given to the imagesin the top-to-down, left-to-right, and oblique directions.

FIG. 5 is a graph for explaining an example of a convergencedetermination method according to this embodiment, and showing therelationship between the number N, of the fine alignment processperformed and an absolute value D, of the deviation amount. A line ofthe FOV indicates a reference value determined on the basis of the sizeof the FOV, and the line can be set in advance, and can also be altered.As the number N of the fine alignment process performed increases, theabsolute value D decreases and comes to converge. Any type ofconvergence determination method can be used in this embodiment. As asimple example, the convergence is determined to be completed when theabsolute value D becomes equal to or less than the predetermined FOVvalue. Nevertheless, this is not to determine that the absolute value Dof the deviation amount has truly converged. Thus, even when the FOVvalue is set to be smaller, it might be determined that the absolutevalue of the deviation amount has converged, although it has not. Thus,even when the absolute value D of the deviation amount becomes equal toor less than the predetermined FOV value, it is necessary to furtherperform several measurements or several tens of measurements until thedeviation amount would be determined to substantially converge, and thenthe convergence should be determined to be completed.

As another example, it is possible to use an algorithm to determine thatthe convergence has been completed when the ratio of a measureddeviation amount D_(n) to a deviation amount D_(n−1) measuredimmediately before the measurement of D_(n) is equal to or less than aset value ε as represented by the following Formula (4). In order tofurther improve the accuracy, it is possible to add a condition thatD_(n) is equal to or less than a certain value, or to add a condition todetermine that the deviation amount has converged when Formula (4) isconsecutively satisfied by a certain number of times.D _(n) /D _(n−1)<ε  (4)

For example, in FIG. 5 showing the relationship between the number N ofthe fine alignment process performed and the deviation amount D, when itis determined that the convergence has been completed at N_(i+1) (thelast plot shown by black circle), the FOV of the ADR is set equal to orabove D_(i+1) corresponding to N_(i+1). The fine alignment process isthen terminated, and the ADR can be performed. In this manner accordingto Formula (4), the processing is simplified because it is possible todetermine that the convergence has been completed in a case where thedeviation amount becomes equal to or less than a certain value, forexample a case where the ratio of the deviation amount D_(n), when theconvergence condition is measured, to the deviation amount D_(n−1)measured immediately before the measurement of D_(n) is equal to or lessthan the set value ε, or in a case where the above condition isrecognized several times. Moreover, there is another advantage that,even when a variation in the deviation amounts is large and theconvergence value is unknown, the processing is further simplifiedbecause the FOV of the ADR can be set to be approximate to theconvergence value.

FIG. 6 shows an example of a GUI for checking a FOV which isautomatically set by analyzing the fine alignment result, and formanually setting a FOV. In the screen, the FOV is displayed as a marklike a straight line or a circle, and it is possible to set a FOV inadvance, or to alter the position thereof. Reference numeral 601 in FIG.6 denotes a screen (corresponding to the reference numeral 115 in FIG.1), and displays a graph showing the relationship between the deviationamount and the number of times of the fine alignment. In the graph, adeviation amount 602 at each measurement point, a convergence value 603of the deviation amounts, and a FOV 604 are shown. The setting of theFOV 604 can be altered by a drag-and-drop operation using a pointingdevice such as a mouse, or by a scroll button (▴ or ▾ in the drawing). Ascreen 605 displays a graph showing a change in the deviation amountbefore and after the coordinate correcting expression optimization.Specifically, the screen 605 displays a FOV 606 and both of deviationamounts 607 at each measurement point before the coordinate correctingexpression optimization and deviation amounts 608 at each measurementpoint after the coordinate correcting expression optimization. Thedeviation amount 607 is shown by a white circle ∘, and the deviationamount 608 is shown by a black circle ●. A dashed line 609 indicates aconvergence value corresponding to the convergence value 603 of thedeviation amounts. It is found that the deviation amounts after thecoordinate correcting expression optimization are settled equal to orbelow the convergence value. The setting of the FOV 606 can be alteredby a drag-and-drop operation using a pointing device such as a mouse, orby a scroll button (▴ or ▾ in the drawing).

A table 610 displays a convergence value of the deviation amounts and aFOV 611. As to the FOV 611, a numerical value can be inputted andupdated using an input device such as a keyboard. The FOV 604 on thescreen 601, the FOV 606 on the screen 605, and the FOV 611 in the table610 are connected with one another, and therefore the result of alteringthe setting for any one of these parameters is automatically reflectedto the other two parameters. A table 612 displays a minimum defect size613 to be detected by the ADR, and a maximum FOV value in each imagesize, the maximum FOV value being calculated on the basis of therelationship between the minimum defect size 613 and the imageprocessing performance.

As to the minimum defect size 613, a numerical value can be inputted andupdated using an input device such as a keyboard. For example, in a casewhere the present apparatus has an image processing performance todetect a difference of 3 or more pixels, and where the minimum defectsize is set to 30 nm, it is possible to detect the difference of 10 nmper pixel. Accordingly, it is possible to calculate that the maximum FOVis: 5.2 μm when the image size is 512×512 pixels; 7.7 μm when the imagesize is 768×768 pixels; and 10.3 μm when the image size is 1024×1024pixels.

Generally, since a smaller image size may shorten the time for defectdetection processing by the ADR, an image size which meets the set FOVand has a minimum number of pixels is selected. In FIG. 6, it isadvantageous to select the image size of 512×512 pixels in terms ofthroughput.

Incidentally, among the screens shown in FIG. 6, it is not alwaysnecessary to prepare all of these, and is only necessary to set at leastany one of: the graph on the screen 601 showing the relationship betweenthe deviation amount and the number of times of fine alignment process;the graph on the screen 605 showing a change in the deviation amountsbefore and after the coordinate correcting expression optimization; theconvergence value of the deviation amounts and the FOV 611 in the table610; and the maximum FOV value in each image size in the table 612.Alternatively, displaying of these screens may be altered by switchingthese screens one after another.

As has been described thus far, according to this embodiment, themeasurement for the coordinate correcting expression optimization isterminated once the deviation amounts converge by using the coordinatecorrecting expression. Thereby, it is possible to suppress the reductionin the throughput to the minimum level. Furthermore, a FOV which isnecessary for a specimen to be within the field of view is automaticallyset according to the calculated convergence value of the deviationamounts. Thereby, it is possible to reduce the frequency of failure indetecting specimen positions caused by an incident that the specimen isnot within the field of view at the time of performing the ADR.

The present invention further includes the following aspects.

-   11. A defect review apparatus for reviewing a defect on a specimen    includes:

an optical detector which detects the defect on the basis of informationon coordinates of the defect, the information transmitted from anexternal apparatus; and

a calculator which calculates a difference in coordinates between theinformation on the coordinates and coordinates of the detected defect,and which compares the difference with a predetermined value.

-   12. In the defect review apparatus as set forth in 11, the    calculator determines to continue the calculation of the difference    when the value of the difference is smaller than the predetermined    value.-   13. In the defect review apparatus as set forth in 11, the    calculator determines whether to stop the calculation of the    difference when the value of the difference is smaller than the    predetermined value.-   14. In the defect review apparatus as set forth in 11, the    calculator stops the calculation of the difference when the value of    the difference is smaller than the predetermined value.-   15. A defect review apparatus for reviewing a defect on a specimen    includes:

a display device which displays an image of the specimen together with amark showing a size of a field of view;

an optical detector which detects the defect on the basis of informationon coordinates of the defect, the information transmitted from anexternal apparatus; and

a calculator which calculates a difference in coordinates between theinformation on the coordinates and coordinates of the detected defect,and which compares the difference with a reference value determined onthe basis of the size of the field of view.

-   16. In the defect review apparatus as set forth in 15, the    calculation of the difference is determined to be continued when the    value of the difference calculated by the calculator is within the    reference value determined on the basis of the size of the field of    view.-   17. In the defect review apparatus as set forth in 16, the reference    value can be altered.-   18. In the defect review apparatus as set forth in 15, whether to    stop the calculation of the difference is determined when the value    of the difference calculated by the calculator is within the    reference value determined on the basis of the size of the field of    view.-   19. In the defect review apparatus as set forth in 18, the reference    value can be altered.-   20. In the defect review apparatus as set forth in 15, the    calculation of the difference is stopped when the value of the    difference calculated by the calculator is within the reference    value determined on the basis of the size of the field of view.-   21. In the defect review apparatus as set forth in 20, the reference    value can be altered.-   22. A defect review apparatus for reviewing a defect on a specimen    includes:

a display device which displays an image of the specimen;

an optical detector which detects the defect on the basis of informationon coordinates of the defect, the information transmitted from anexternal apparatus; and

a calculator which calculates a difference in coordinates between theinformation on the coordinates and coordinates of the detected defect,wherein the calculator determines to continue the calculation of thedifference depending on whether or not the defect appears in the imageof the specimen displayed on the display.

-   23. In the defect review apparatus as set forth in 22, the    calculator stops continuing the calculation of the difference when    the defect appears in the image of the specimen displayed on the    display.-   24. In the defect review apparatus as set forth in 22, the    calculator causes the display to display a mark indicating a    reference for the determination whether to continue the calculation    of the difference.-   25. In the defect review apparatus as set forth in 24, a position of    the mark can be altered.-   26. In the defect review apparatus as set forth in 22, when the    defect does not appear in the image of the specimen displayed on the    display, an image of a region adjacent to the image of the specimen    is captured, and this capturing is repeated until the defect    appears.-   27. A defect review apparatus for reviewing a defect on a specimen    includes:

an input unit which receives information on coordinates of the defect,the information transmitted from an external apparatus;

a calculator which executes a desired calculation on the basis of atleast the information on the coordinates; and

a display unit which displays a result of the calculation executed bythe calculator, wherein the calculator causes the display unit todisplay a change in the degree of a difference between the coordinatesof the information and coordinates of the defect detected on the basisof the information on the coordinates.

-   28. In the defect review apparatus as set forth in 27, the    calculator causes the display unit to display the degree of the    difference when the change in the degree of the difference becomes    smaller than a predetermined value.-   29. A defect review apparatus for reviewing a defect on a specimen    includes:

an input unit which receives information transmitted from an externalapparatus;

a calculator which executes a desired calculation on the basis of atleast the information; and

a display unit which displays a result of the calculation executed bythe calculator, wherein:

the input unit receives coordinates of a targeted position on thespecimen, the coordinates transmitted from the external apparatus, and

when the coordinates of the targeted position on the specimen, which istransmitted from the external apparatus, are provided in a plurality andare set as first coordinates, and when a plurality of coordinates oftargeted positions which correspond to the targeted positions on thespecimen disposed on a stage, are set as second coordinates, thecalculator corrects the second coordinates to reduce a differencebetween the first coordinates and the second coordinates, and repeatsthe correction of the second coordinates to reduce an error, and

when it is determined that the difference has converged, the calculatorcauses the display unit to display a result of the convergence.

-   30. In the defect review apparatus as set forth in 29, the display    unit displays a determination value for determining that the    difference has converged.-   31. In the defect review apparatus as set forth in 29, the    calculator determines, on the basis of the result of the convergence    of the difference, an image magnification for reviewing the targeted    position and a FOV.-   32. In the defect review apparatus as set forth in 31, the display    unit displays the image magnification and the FOV determined by the    calculator.

1. A defect review apparatus for reviewing a defect on a specimen whoseposition is specified in a second coordinate system after the specimenis moved to a pre-calculated coordinate position in a first coordinatesystem, the apparatus comprising: a deviation-amount measurement unitwhich measures a deviation amount between the pre-calculated coordinateposition and an actual position of the specimen; acoordinate-correcting-expression optimizing unit which optimizes acoordinate correcting expression for converting the second coordinatesystem to the first coordinate system so as to minimize the measureddeviation amount; and a deviation-amount-convergence determination unitwhich determines that the deviation amount has converged, wherein, themeasurement for optimizing the coordinate correcting expression isterminated when the deviation amount has converged.
 2. The defect reviewapparatus according to claim 1, further comprising a field of view (FOV)automatic setting unit which calculates a required pixel size on thebasis of a convergence value of the deviation amount so that therequired pixel size is as small as possible among sizes allowing thespecimen to be within the FOV, and which automatically sets the FOV onthe basis of the required pixel size.
 3. The defect review apparatusaccording to claim 2, wherein the coordinate-correcting-expressionoptimizing unit continues the measurement for optimizing the coordinatecorrecting expression when the FOV calculated on the basis of theconvergence value of the deviation amount cannot be set by a minimummagnification required for detecting the position of the specimen. 4.The defect review apparatus according to claim 2, wherein the FOVautomatic setting unit divides a field of view for detecting theposition of the specimen into a plurality of areas when the FOVcalculated on the basis of the convergence value of the deviation amountcannot be set by a minimum magnification required for detecting theposition of the specimen.
 5. The defect review apparatus according toclaim 1, further comprising a display controller which performs acontrol to display in parallel a plurality of items selected from: afirst measurement result showing a relationship between the number oftimes of fine alignment process and the deviation amount at eachmeasurement point; a second measurement result showing a change in thedeviation amounts before and after the coordinate correcting expressionoptimization; a third measurement result showing a relationship betweena convergence value of the deviation amount and a field of view (FOV);and a fourth measurement result showing a minimum defect size to bedetected as well as a maximum FOV value in each image size, the maximumFOV value being calculated on the basis of a relationship between theminimum defect size and an image processing performance.
 6. A defectreview apparatus for reviewing a defect on a specimen by moving thespecimen to a pre-calculated coordinate position in a first coordinatesystem to specify a position of the specimen by a second coordinatesystem, the apparatus comprising: a deviation-amount measurement unitwhich measures a deviation amount between the pre-calculated coordinateposition and an actual position of the specimen; acoordinate-correcting-expression optimizing unit which optimizes acoordinate correcting expression for converting the second coordinatesystem to the first coordinate system so as to minimize the measureddeviation amount; and a deviation-amount-convergence determination unitwhich determines that the deviation amount has converged, wherein,measurement for optimizing the coordinate correcting expression isterminated at a time when a convergence value of the deviation amountbecomes equal to or less than a predetermined value.
 7. The defectreview apparatus according to claim 6, wherein thecoordinate-correcting-expression optimizing unit continues themeasurement for optimizing the coordinate correcting expression when thesize of a field of view (FOV) for reviewing calculated on the basis ofthe convergence value of the deviation amount is not settable, even witha minimum required magnification for detecting the position of thespecimen.
 8. The defect review apparatus according to claim 6, wherein afield of view (FOV) automatic setting unit divides a field of view fordetecting the position of the specimen into a plurality of areas whenthe FOV calculated on the basis of the convergence value of thedeviation amount is not settable even with a minimum requiredmagnification for detecting the position of the specimen.
 9. A method ofreviewing a defect on a specimen by moving the specimen to apre-calculated coordinate position in a first coordinate system tospecify a position of the specimen by a second coordinate system, themethod, which is performed by a computer of a defect review apparatus,comprising the following steps of: measuring a deviation amount betweenthe coordinate position in the first coordinate system and a coordinateposition in the second coordinate system, and starting a fine alignmentprocess for optimizing a coordinate correcting expression so as tominimize the deviation amount; iteratively performing a procedure foroptimizing the coordinate correcting expression and concurrently formeasuring a deviation between coordinates corrected on the basis of thecoordinate correcting expression and coordinates of a position of thespecimen actually detected; determining whether the deviation amount hasconverged; and continuing the fine alignment process when the deviationamount has not converged, or setting a field of view (FOV) to be equalto or greater than a convergence value; and terminating the finealignment process, when the deviation amount has converged.
 10. Themethod of reviewing a defect according to claim 9, further comprisingthe steps of, comparing the convergence value of the deviation amountwith a FOV in terms of size; and terminating the fine alignment processwhen the convergence value of the deviation amount is equal to or lessthan the FOV, and enlarging the FOV with a reviewing magnificationmaintained when the convergence value is greater than the set FOV.
 11. Anon-transitory computer readable medium encoded with a program which,when loaded into a computer of a defect review apparatus that alsoincludes a deviation measurement device, causes the apparatus to performthe following steps: said deviation measurement device measuring adeviation amount between the coordinate position in the first coordinatesystem and a coordinate position in the second coordinate system, andstarting a fine alignment process for optimizing a coordinate correctingexpression so as to minimize the deviation amount; iterativelyperforming a procedure for optimizing the coordinate correctingexpression and concurrently for measuring a deviation betweencoordinates corrected on the basis of the coordinate correctingexpression and coordinates of a position of the specimen actuallydetected; determining whether the deviation amount has converged; andcontinuing the fine alignment process when the deviation amount has notconverged, or setting a field of view (FOV) to be equal to or greaterthan a convergence value; and terminating the fine alignment process,when the deviation amount has converged.
 12. The non-transitory computerreadable medium according to claim 11, wherein said program furthercomprise the following steps: comparing the convergence value of thedeviation amount with a FOV in terms of size; and terminating the finealignment process when the convergence value of the deviation amount isequal to or less than the FOV, and enlarging the FOV with a reviewingmagnification maintained when the convergence value is greater than theset FOV.